Project Habakkuk was an ill-fated projected designed to harness natural resources into weapons of war. It did not go well.

In 1942, British ships were facing major threats from German U-Boats. Supplies were scarce, and German submarines were taking down British supply ships, preventing them from reaching their final destinations. British planes provided effective cover for the supply ships but were limited in how far they could travel over open ocean without needing to land and refuel. Seaborne aircraft carriers were needed to provide planes a place to land, but building traditional aircraft carriers required large amounts of resources, especially steel, which were already in short supply.

Geoffrey Pyke was a British inventor, at that time working at the Combined Operations Headquarters under Lord Louis Mountbatten. He had first been assigned to work on Project Plough, which aimed to create an elite fighting force capable of doing battle in harsh winter conditions of snow and ice. With glacial conditions already on his mind, Pyke turned his mind to the problem of seaborne landing.

He consulted Max Perutz, an Austrian-born biologist who had previously worked studying glaciers, and together, they devised a plan to create aircraft carriers that would not tax Britain’s already strained resources. Pyke theorized that aircraft carriers could be made of hollowed-out icebergs, which would be durable, buoyant, easy to produce without a lot of resources, and easily repairable if damaged by the enemy.

Pyke brought his solution to Mountbatten, who proposed the idea of Winston Churchill. He approved the idea, code-naming it Project Habakkuk, a reference to the biblical book of Habakkuk: “… be utterly amazed, for I am going to do something in your days that you would not believe, even if you were told.” (Habakkuk 1:5, NIV)

At first, Project Habakkuk seemed like a lost cause. While ice was strong, it was also too brittle to hold up its own weight and easily lost shape under pressure. Ice also melts, which required Pyke to develop a complex cooling system that continuously pumped refrigerant throughout the carrier to keep it frozen.

However, Pyke then discovered pykrete, a mixture of wood pulp and ice, which was stronger and more malleable than ice. The wood pulp created an insulating shell around the exterior of the material that was found to be resilient to bullets and artillery shelling.

With this new discovery, they decided to build a pykrete prototype in Patricia Lake, Alberta to test the effectiveness on a large scale model. However, even with the new pykrete discovery, the plan still faced large problems.

The prototype required a constant refrigeration system to keep cool. If the temperature of the shop dropped below three degrees Fahrenheit, it would start to sag and lose shape. Although the pykrete mixture made the prototype stronger than ice, it also required much more insulation.

Steel would still have been needed to insulate the carrier, which would have drained more resources and made it still more expensive, while the increased size would have made it slow and difficult to maneuver. Wood was also in short supply during the war, and building a pykrete aircraft carrier would have negatively impacted paper production.

As good as it might have sounded on paper, the prototype proved it was too impractical to implement, and Pyke and his team were eventually forced to abandon the idea. The British turned their attention to more practical projects, and the remains of the prototype, and an underwater plaque, still lie under the bottom of Patricia Lake.

Along with the hope of Project Habakkuk.

Scale model of Project Habakkuk Aircraft carrier :

The decision was made to build a large-scale model at Jasper National Park in Canada to examine insulation and refrigeration techniques, and to see how pykrete would stand up to artillery and explosives. Large ice blocks were constructed at Lake Louise, Alberta, and a small prototype was constructed at Patricia Lake, Alberta, measuring only 60 by 30 feet, weighing 1,000 tons and kept frozen by a one-horsepower motor.

The work was done by conscientious objectors who did alternative service of various kinds instead of military service. They were never told what they were building. Bernal informed COHQ that the Canadians were building a 1,000-ton model, and that it was expected to take eight men fourteen days to build it. The Chief of Combined Operations (CCO) responded that Churchill had invited the Chiefs of Staff Committee to arrange for an order to be placed for one complete ship at once, with the highest priority, and that further ships were to be ordered immediately if it appeared that the scheme was certain of success.

The Canadians were confident about constructing a vessel for 1944. The necessary materials were available to them in the form of 300,000 tons of wood pulp, 25,000 tons of fibreboard insulation, 35,000 tons of timber and 10,000 tons of steel. The cost was estimated at £700,000.

Meanwhile, Perutz had determined via his experiments at Smithfield Market that the optimum structural properties were given by a mixture of 14 percent wood pulp and 86 percent water. He wrote to Pyke in early April 1943 and pointed out that if certain tests were not completed in May, there would be no chance of delivering a completed ship in 1944.

By May the problem of cold flow had become serious and it was obvious that more steel reinforcement would be needed, as well as a more effective insulating skin around the vessel’s hull. This caused the cost estimate to increase to £2.5 million. In addition, the Canadians had decided that it was impractical to attempt the project “this coming season”. Bernal and Pyke were forced to conclude that no Habakkuk vessel would be ready in 1944.

Pyke was excluded from the planning for Habakkuk in an effort to secure American participation, a decision that Bernal supported. Pyke’s earlier disagreements with American personnel on Project Plough, which had caused his removal from that project, were the main factor in this decision.

Naval architects and engineers continued to work on Habakkuk with Bernal and Perutz during the summer of 1943. The requirements for the vessel became more demanding: it had to have a range of 7,000 miles (11,000 km) and be able to withstand the largest waves recorded, and the Admiralty wanted it to be torpedo-proof, which meant that the hull had to be at least 40 ft (12 m) thick. The Fleet Air Arm decided that heavy bombers should be able to take off from it, which meant that the deck had to be 2,000 ft (610 m) long. Steering also raised problems; it was initially projected that the ship would be steered by varying the speed of the motors on either side, but the Royal Navy decided that a rudder was essential. However, the problem of mounting and controlling a rudder over 100 ft (30 m) high was never solved.

Variants of Project Habakkuk Aircraft carrier

Naval architects produced three alternative versions of Pyke’s original concept, which were discussed at a meeting with the Chiefs of Staff in August 1943:

Habakkuk I (soon discarded) would have been made of wood.

Habakkuk II was closest to the COHQ model and would have been a very large, slow, self-propelled vessel made of pykrete with steel reinforcement. The size would have been a length of 1200 meters and a width of 180 meters.

Habakkuk III was a smaller, faster version of Habakkuk II.

Air Chief Marshal Portal asked about potential bomb damage to Habakkuk III, and Bernal suggested that a certain amount of deck covering might be ripped off, but could be repaired by some kind of flexible matting. It would be more difficult to deal with bomb holes in the center portion, through the roof over the aircraft hangars would be made proof against 1,000 kg bombs. Bernal considered that no one could say whether the larger Habakkuk II was a practical proposition until a large-scale model could be completed and tested in Canada in the spring of 1944. He had no doubts about the suitability of pykrete as a material but said that constructional and navigational difficulties remained to be overcome.

The final design of Habakkuk II gave the bergship (as it was called) a displacement of 2.2 million tons. Steam turbogenerators were to supply 33,000 hp (25,000 kW) for 26 electric motors mounted in separate external nacelles (normal, internal ship engines would have generated too much heat for an ice craft). Its armament would have included 40 dual-barrelled 4.5″ DP (dual-purpose) turrets and numerous light anti-aircraft guns, and it would have housed an airstrip and up to 150 twin-engined bombers or fighters

End of Project Habakkuk

By the time of the 1943 Quebec Conference the Habakkuk project had won the support of both Churchill and Mountbatten and was assigned to the National Research Council of Canada because of the cold Canadian winters and Canadians’ prior familiarity with ice physics. The small prototype built in 1944 on a lake near Jasper, Alberta, confirmed the researchers’ forecast that the full-size vessel would cost more money and machinery than a whole fleet of conventional aircraft carriers. NRC President C.J. Mackenzie later said British promoters of Habakkuk were so intimidated by Prime Minister Churchill that they kept this information from him until the Canadian’s next visit to Britain.[ Mountbatten later listed several points:

Demand for steel for other purposes was too great.

Permission had been received from Portugal to use airfields in the Azores, which facilitated the hunting of U-boats in the Atlantic

The introduction of long-range fuel tanks allowed British-based aircraft extra patrol time over the Atlantic

The numbers of escort carriers were being increased.

In addition, Mountbatten himself withdrew from the project.

The final meeting of the Habakkuk board took place in December 1943. It was officially concluded that “The large Habbakuk II made of pykrete has been found to be impractical because of the enormous production resources required and technical difficulties involved.”

The use of ice had actually been falling out of favor before that, and other ideas for “floating islands” had been considered, such as welding Liberty Ships or landing craft together (Project TENTACLE). It took three hot summers to completely melt the prototype constructed in Canada.

Perutz wrote that he stayed in Washington D.C. while U.S. Navy engineers evaluated the viability of Habakkuk. He concluded: “The U.S. Navy finally decided that Habakkuk was a false prophet. One reason was [that] the enormous amount of steel needed for the refrigeration plant that was to freeze the pykrete was greater than that needed to build the entire carrier of steel, but the crucial argument was that the rapidly increasing range of land-based aircraft rendered floating islands unnecessary.

Criticism on Project Habakkuk

The Habakkuk design received criticism, notably from Sir Charles Goodeve, Assistant Controller of Research and Development for the Admiralty during the Second World War. In an article published after the war, Goodeve pointed out the large amount of wood pulp that would be required was enough to affect paper production significantly. He also claimed that each ship would require 40,000 tons of cork insulation, thousands of miles of steel tubing for brine circulation and four power stations, but that for all those resources (some of which could be used to manufacture conventional ships of more effective fighting power) Habakkuk would be capable of travelling at only six knots of speed. His article also contained extensive derisive comments about the properties of ice as used for ship construction.